Hydraulic power transmission system



Aug. 8, 1944.

H. w. ADAMS ETAL 2,355,357 HYDRAULIC POWER TRANSMISSION SYSTEM 3 Sheets-Sheet 1 Filed March 20, 1939 INVENTORS. HAROLD W ADAMS EARL 5. KLE/NHANS fiaa wzb A TTORNEY.

u 8 E944. H. w. ADAMS E'EAL 2,355,357

HYDRAULIC POWER TRANSMISSION SYSTEM Filed March 20, 1939' 3 Sheets-She'et 2 INVENTORS. HAROLD W ADAMS EARL S. KLE/NHANS ATTORNEY Aug. 8, 1944- H. w. ADAMS ETAL HYDRAULIC POWER TRANSMISSION SYSTEM I Filed March 20, 1939 5 Sheets-Sheet 3 6 INVENTORS. HAROLD VV. ADAMS EARL. KLE/NHAN5 ATTORNEY.

stantially constant speed prime mover.

Patented Aug. 8, 1944 UNITED STATES PATENT OFFICE HYDRAULIC POWER TRANSDHSSION SYSTEM Harold W. Adams and Earl Schuyler Kleinhans, Santa Monica, Calif., assignors to Douglas Air- (czrzgft Company, Incorporated, Santa Monica,

Application March 20, 1939, Serial No. 262,958

6 Claims.

Our invention relates to a hydraulic transmission system in which pressure fluid is supplied by one or more pumps and is utilized to operate various power transforming units. It has great utility in. any installation where it is desired to operate several diflerent types of equipment -quently in locations where it is almost impossible to reach them, with a mechanical drive. Where the units to be operated have widely different characteristics, such as a constant speed unit, a variable speed unit and a constant torque unit the dimculty of operating them all from a single source of power is obvious.

, Electrical systems overcome some of these disadvantages but have other difficulties of their own. Electric generators normally require a sub- In a moving vehicle, such as an automobile, train or airplane, the driving engine, or prime mover, necessarily runs at a wide range of speeds and is not suitable for driving an electrical generator which is to supply p wer to anything besides a battery. Hence a separate prime mover is necessary. This adds weight and complication as well as an additional source of possible mechanical failure. Each of the units operated by the electrical system develops'heat which must be dissipated at the source. This necessitates as many cooling systems as there are driven units.

Hydraulic systems can be designed to obviate allthe difliculties mentioned above and have advantages not obtainable with mechanical or electrical systems. While hydraulic power transmission systems generally are old, we are not aware of any which incorporate the novel features of our invention.

In general the hydraulic system of our invent'on includes a prime mover, which in the case of a moving vehicle comprises a variable speed motor, a variable delivery hydraulic pump driven by the motor and drawing liquid from a sump or reservoir, a plurality of hydraulically as constant speed, variable speed and the like. a conduit system extending between the'source of power and the driven units, and a pressure fluid accumulator connected to the conduit system for absorbing shock and surge resulting from variation in the demand of the driven units.

A sump or reservoir is provided which is dedesigned to de-aerate the liquid of the hydraulic system by centrifugal force. The sump is also provided with a novel selector valve system for controlling the flow of fluid to any one of several umps. Leakage of a pump or its associated piping is detected by a float responsive to the liquid level in the sump, the float being adapted to operate a valve to shut oi! the supply of liquid to the defective pump system.

One of the many advantages of our system is that the heat losses resulting from generation and transmission of energy may be transferred by the hydraulic fluid to a single point, and a single cooling system can therefore serve all the auxilaries.

It is apparent that any number of sources of supply of fluid pressure may be used. In the case of a multl-engined aircraft for example. each of the engines can operate a variable delivery fluid pump and all the pumps can be condriven units having difierent characteristics such nected to-the same systems so that if any one pump is operating properly there will be an adequate supply of power for the entire group of auxiliaries.

One of the objects of the invention is to provide a substantially unitary power transmission system for operating all auxiliaries, particularly in moving vehicles.

Another object is to provide a power transmission which may operate successfully from any one of several sources of supply.

Another object is to provide a power transmission system which may supply power to relatively inaccessible driven units.

Another object is to provide a unitary power transmission system which is adapted to operate driven units having basically different operating characteristics.

Another object is to provide a power transmission system which simplifles the problem of cooling a plurality of driven units.

Other and further objects and advantages will become apparent as the description proceeds.

The invention is capable of embodiment in a variety of forms, some of which are illustrated in the accompanying drawings, wherein:

Figure 1 is a schematic diagram of one embodiment of the invention, showing a complete unitary hydraulic transmission system;

Figure 2 is a section taken at line t--2 of Figure 1 and showing the means for de-aerating the hydraulic fluid;

Figure 3 is an enlarged section taken at line 3-3 of Figure 1 and showing the internal construction of the pressure fluid accumulator;

Figure 4 is an elevational view, partly in section, showing details of a'turbine, an alternator driven thereby, a governor for the turbine, and the fluid sump including its selector valves and cooling system;

Figure 5 is a detailed view of one selector valve of Figure 4, viewed from'line -E of Figure 4, and indicating four float controlled positions of said valve in a two valve selector system; and

Figure 6 is a detailed view of a second selector valve of Figure 4, viewed from line 6-5 of Figure 4, and indicating four float controlled positions of said valve in a two valve selector system.

Referring now to the drawings:

Figure 1 shows a complete unitary hydraulic system, including prime movers ll, l l, which may be main engines of a multi-engined airplane,

v fluid pumps l0, Ill driven by the prime movers, a.

fluid conduit system it, it, a pressure fluid accumulator 26, connected to the conduit system, hydraulically driven units, such as It, It and I5, sump l2, and fluid return conduits lzd and .021.

Since the prime movers may be driven at any speed throughout a wide range and one or more may be operating while some are idle, and the demands of the systems may vary without relation to the operation of the prime movers, the pumps Ill and Ill must be capable of supplying varying amounts of fluid at any desired pressure while being driven at any speed, and must all be connected to the same conduit system. The type of pump to be used may be one which discharges a constant volume of liquid at any desired pressure, the excess liquid being by-passed to a sump, or one in which the output is varied by throttling of the intake, or one which is designed to operate with'variable displacement, supplying the desired volume of liquid at all times at a predetermined constant pressure. This last type is the one preferred for use in our system at the present time.

Conduits l6 and I6 convey the pressure fluid from the variable delivery pumps to the remainder of the system and are interconnected at I35 so that either conduit can supply the entire system. The supply to any particular unit of the system may be regulated or shut off by means of conventional valves, It, I3, 253, ll. If the ressure in the system should become excessive for any reason it may be relieved by a safety valve 22 of any desired type the liquid flowing therethrough to return pipe 2. Check valves l1 and i1 serve to prevent return flow from the main system to any of the pumps in case any pump is not operating or its associated piping fails.

A pressure fluid accumulator 26 is incorporated in the conduit system for smoothing out surges and shocks and for supplying a limited amount of pressure fluid to operate auxiliaries when all pumps are idle. This accumulator is preferably but not necessarily located near the motors and their associated pumps.

.The construction of the accumulator is shown in detail in Figure 3. It is in effect a dual pressure tank made up of two dome-like shells El and 2d fastened together around their periphery by any suitable means, such as bolts 29 and nuts 36. These shells are shown as substantially hemispherical in the drawings but obviously may be of any other desired shape which is suitable to withstand the high pressure'in the system which may be of the order of 1500 pounds per square inch. A diaphragm 33 having suitable elastic and oil resisting properties is used to separate the tank into a primary chamber 3 and a secondary chamber 35 and to prevent the air from mixing with the liquid. The diaphragm is provided with a circumferential bead which is secured within grooves or recesses formed in the meeting faces-of the shells. Shell 2? is provided with a port M for entry of air. A check valve as is threadedly engaged in the port 3i so that air or other gas may be supplied to chamber 3% and stored therein under pressure. Shell is is provided with a port 32 which is connected by means of fitting so to the main hydraulic system.

In practice air is stored in chamber 3% under several hundred pounds pressure. Liquid is then supplied to chamber 35 and subjected to the pressure of the main system. Positive pressure surges will be transmitted to the liquid in chamber 35 which chamber will consequently increase in volume, compressing the air in chamber 3 3 and increasing its pressure. As the surge dies down the diaphragm will return to its normal position and the chambers will regain their normal relative volumes. A negative pressure surge will cause the reverse action, as is apparent. It can be seen that the pressure fluid accumulator thus serves to prevent shocks which might otherwise damage the hydraulic system.

The accumulator also serves as an emergency source of pressure fluid in the event of complete failure of the power-plants or of the pumps. For instance in case of a forced landing of an airplane, it may be used to extend the landing gear, maintain the lighting system in operation, or actuate any safety device with which the airplane may be equipped. It may also serve as a source of supply for operating hydraulic engine starters, etc. Since the air in chamber 3% is under a high initial pressure it may be used to force the oil out of chamber 35 until the entire volume is used up, as indicated by the dotted line position of the diaphragm in Figure 3.

An important feature is the provision of the valve members ll and A2 in Figure 3. These are attached to the opposite faces of the diaphragm substantially at its center. They may be made of metal or other high strength material. If the diaphragm is forced against either of the vents 3! and 32 during operation the members il and 42 will prevent the material of the diaphragm itself from being forced into the vents and thus avoid possible damage. Moreover, should a leak develop in check valve 39 accompanied by some leakage through the diaphragm, member M will seat around and seal the vent 3i thus preventing connected to the v motion causing similar and for the orifice is a mechanical comprising a linkage, member 88 of which is.

member 90 pivoted at 9| phragm must be ofhish quality material and accurately dimensioned. In the dlaphragms now in use the thickness at diametrically opposite points is maintained the same within .005 inch.

In modern airplanes and other vehicles various constant speed mechanisms are employed. For

instance'alternating current is coming into use 'and it is desirable to maintain the speed of the Theunit pressure acting upon the areas being substantially uniform when pressure acts upon the piston, the needle tends to reduce the orifice,

but when pressure is effective-upon the needle only, the needle tends to increase the orifice, the liquid in the cylinder returning through the valve body to the sump reservoir, and motion of the alternating current generatorsas constant as possible.

In order to attain the desireddegree of accurate regulation of such constant speed units as the alternator 43, a mechanically-hydraulically operable governing unit, the preferred embodiment of which is shown in section Figure 4, can be used advantageously. The liquid enters a' nozzle body 46 through a pressure line 41 and a fitting 48 and passes through the body and orifice 49 thereof to drive the turbine l3, there being a longitudinally movable needle 50 for adjusting the size of the Attached to the turbine shaft is a conventional governor 52 the fiy-balls 53 of which are cooperable with an inner sleeve 51 of a valve body 58 so that radially outward movement of the balls causes the inner sleeve to move away from the governor, motion toward the governor being obtained by aspring return 59. The inner sleeve has three, ports, a liquid pressure inlet 60, a liquid return GI and a bleed port 62 on the opposite side of .the pressure inletfrom the return. Within the valve body and enc'asing the inner sleeve, is an outer sleeve 63 which has four ports, an inlet port 64 cooperable with inlet port BOthrough a passageway 65, a return 'return port 6| 60 and of-both inner and outer sleeves through a passageway 11 in the valve body. Pressure liquid is also led from the operating port of theouter sleeve successively through a passageway !8 of the valve body, a fitting threadably a lve body, duit 80 and a fitting 8| threadably connected to an auxiliary nozzle member 82, and to a piston 83 and cylinder in the nozzle body 46, piston proportional needle hydraulic control follow-up device B motion. Supplementing the pivoted at 89 to a fixed support not shown, and to a support also not shown,-and operatively connected-to the outer sleeve through an opening 92 in the valve body and also by a rod 93 to the needle 58. The cross sectional area of the rod subtracted from the cross sectional area of the piston equals the effective pressure area 'at the back of the needle, which area is greater than that of the needle itself.

an operating con-- needle causing the linkage to move the outer sleeve in a direction, and-distance conforming with the initial movement of the inner sleeve.

In Figure4, the governing system is shown in a position of stability, wherein the alternator load and therefore the speed of the turbine are constant, the position of the needle relative to the orifice is fixed, the mechanical governor has attained a neutral position, and liquid is trapped within the entry-ports of both inner and outer sleeves as well as in the conduit between the operating passageway of the valve body and the recessed cylinder. When the load upon the alternator decreases, the shaft speed tends to increase causing the governor to move the inner sleeve toward the left thereby valving pressure liquid from inlet. port of the inner sleeve through operating passageway 1| and port 10 of the outer sleeve to the piston and cylinder, the resultant piston travel moving the needle to reduce the orifice. The needle movement actuates the linkage mechanismin a manner such that the land 96 of' the inner sleeve covers the outer sleeve passageway 1 I, thereby shutting off the supply of pressure and retrapping liquid in the conduit between the operating port 10 and the cylinder 84. The back pressure upon the needle tends to re-open the orifice,.which action is prevented by the trapped liquid, and although the position of both sleeves is now changed relative to the valve body, their position relative to each other is again the same, as shown in Figure 4.

When the load upon the alternator increases. the fiy-balls move radially inwardly in response to the tendency of the shaft speed to decrease, the

return spring 59 moves the inner sleeve righta a hydraulic turbine H. The

wardly thereby opening the return port 6| of the inner sleeve to the operating port 10 of the outer sleeve, and the trapped liquid. is returned to the sump reservoir by movement of the-needle in creasing the orifice. The needle movement again actuates the linkage mechanism to retrap liquid between the operating port 10 and the cylinder 84, thereby allowing the needle to remain relativelyfixed at thatparticular setting.

Adifierent type of demand is imposed on the hydraulic system by the cabin supercharger indicated at 44, which is driven in this example by load on the super-' charger and its speed vary with the altitude and the amount of supercharging desired. The rate of fluid flow may be governed manually or automatically depending on the. design requirements.

. Several of the instruments in an airplane, such as a gyro-compass or gyro-pilot, are driven by a suction pump or evacuator, such as centrifugal pump 45. While the load remains substantially constant at all times the speed of the blower must be increased as the air become:- thinner at high altitudes.

Hence such adevice puts a third type of dem'and on the hydraulic system..

Other types of demands on such a system in an airplane would be deicer pump: running at substantially constant speed and load but operated intermittently and retractable landing sure transformer comprising a motor I30 and a pump I3I can be employed to draw liquid from a separate sump reservoir through a conduit I32 and discharge pressure liquid through a conduit I33 to the hydraulic units.

In the system including a plurality of hydraulic motors, a common sump reservoir, which Is vented to the atmosphere as at 91, is pro-.

vided, and there may be return lines as 90 from the motors so positioned that the liquid flows to the sump by force of gravity. There may also be a sump 99 wherefrom liquid is pumped to the sump reservoir by a scavenger pump I driven by a motor IN; and a motor may be so located that the liquid falls straightway into the sump reservoir.

A radiator I04 is associated with the sump :res-

ervoir for governing the liquid temperature, whereby the heat losses in the system can be dissipated at a convenient location. Air from a source not shown is led to and from the radiator through ducts I and I06 within which a thermostatically operable shutter I0! is installed preferably aft of the cooler, the thermostat I00 being located below the liquid level and adapted to actuate the shutter by a link mechanism I09.

As shown in Figure 2, the direction of liquid flow through the return conduits 98 and H2 is substantially tangential to the periphery of the sump reservoir, which arrangement reduces foaming of the liquid within the sump and also expels air from the system, the aeration arising from the normal operation of the turbines.

The system which utilizes a plurality of pumps includes a selector unit H3 whereby liquid flow to the pumps is selectively controlled so that any leaking pump system will shut off as at valve .ports III and 5. An embodiment of the selector valve for a two-pump system shown in Figures 4-5-6 is operable by the liquid level within the sump reservoir, wherein a. float Hi6 is fastened to a rock-shaft III having a single cam H8 and a dual cam II9 arranged in operative relation to faces I20 and I2I of a pair of rods I22 and 2I3 each of which is adapted to actuate a valve I 24 or I25 for controlling a'supply of liquid through a conduit I26 or I21 to one of the pumps I0 or I0, whereby the necessary differentially selective actuation of the valve rods is attained.

Figures 5 and 6 show four positions of the float, A, B, C, and D:

Position A: Cams H8 and H9 are in such positionsrelative to the faces I20 and I2I that valve ports II 4 and H5 are open for liquid flow through conduits I 26 and I2! to the pumps l0 and I0.

Position B: In Figure 5, cam H8 is contacting theface I20 of the aperture in the valve rod thereby maintaining port H4 open, and in Figure 6, the cam 'I I9 has revolved from contact with the face I2l, thereby permitting valve I25 to seat on port II5.

Position C: In Figure 5, single cam Hit has revolved from contact with face I20, thereby permitting valve m to seat on port m and m Figure 6, dual cam IIB has revolved to contact face I2I, thereby unseating valve I25 from port H5.

Position D: Cams H8 and II! have revolved from contact with the faces I20 and I2I 'respectively, thereby permitting valves I20 and I2! to seat-on ports Ill and IIS.

In operation, if the liquid in the sump reservoir falls below the normal level, port II5 closes the conduit I21 leading to a pump system and at least temporarily disccntinues functioning of the respective pump I0. If the level continues to fall: port H4 closesand the .pump I0 ceases to function, port II5 ,re-opens and the initially discontinued pump system resumes operations. If the level continues tov fall; ports IN and H5 will close and functioning of the controlled system will cease pending the-necessary repairs. I

' ly on any one of them, should the others cease to operate for any reason. Our system takes the equivalent of a single power source and transmits it to any number of driven units regardless of the type of demand they impose. It incorporates safety devices and an emergency or reserve source of supply. It eliminates the necessity for individual cooling or ventilation of each of the driven units. It is more compact and convenient and easier to install and maintain than any comparable prior art system of which we are aware. Because of these features it is also lighter in weight and more emcient in operation.

While we have shown a preferred embodiment in considerable detail and described it at length, it is obvious that many changes may be made in the details of construction and specific arrangement of parts without departing from the spirit of the invention and we aim to cover all such changes and modifications in the appended claims.

We claim:

1.. A hydraulic power transmission system in-. cluding a plurality of pump means adapted to supply fluid under pressure, a hydraulically driven unit, sump means and a closed conduit system interconnecting the pump means, the driven unit and the sump means, and selector valve means responsive to the liquid level in the sump and operative to selectively controlthe flow of fluid from the sump means to the pump means. e

2. A hydraulic power transmission system including a plurality of independently operating prime movers operating at widely varying speeds and adapted to drive a vehicle'directly, separate pump means actuated by each of said prime movers and adapted to supply fluid at constant pressure and in variable volume regardless of the speed of their respective prime movers, a hydraulic conduit system interconnecting said pump means, and a plurality of hydraulically driven units operatively connected to said hydraulic system and imposing difierent types of demands thereon, each of the pump means being adapted to supply all demands simultaneously regardless of the operation of any other pump means.

3. A hydraulic power transmission system including a plurality of independently operating prime movers operating at widely varying speeds and adapted to drive a vehicle directly, separate pump means actuated by each of said prime movers and adapted to supply fluid at constant pressure and in variable volume regardless of the speed of their respective prime movers, a hydraulic conduit system interconnecting said pump means, a hydraulic pressure fluid accumulator in operative communication with the fluid in said conduit system, and a plurality of hydraulically driven units operatively connected to said hydraulic system and imposing diil'erent types of demands thereon, each or the pump means being adapted to supply all demands simultaneously regardless of the operation of any other pump means, said accumulator serving to minimize surge and shock resulting from variable operation and also supplying power for emergency operation when all pump means are out of operation.

4. A hydraulic power transmission including a plurality of pump means adapted to supply fluid underpressure, a plurality of hydraulically driven units, sump means connected to said driven units, separate conduits connecting said sump means 5. In a hydraulic power transmission system, a. plurality of interconnected sources of fluid un der pressure, a plurality of isolated hydraulically driven units connected to said sources of fluid under pressure, sump means connected to said units to receive exhaust fluid therefrom, separate conduits for conducting fluid from said sump means to said respective sources of fluid under pressure, a de-aerating means, a heat exchanger and selector valve means being incorporated in said sump, said selector valve means being responsive to liquid level in said sump to control the flow of fluid through said conduits.

6. In a hydraulic power transmission system, a plurality of pump means for supplying fluid under pressure, hydraulically driven motor means, high pressure conduit means connecting the high pressure side of said motor means simultaneously to said plurality of pump means, a sump means connected to the low pressure side of said motor means, separate return conduits connecting said sump means to said plurality of to each of said pump means, and selector valve means'responsive to the liquid level in the sump means and operative to selectively control the return flow or liquid through each of the conduits from the sump means to the pump means.

pump means respectively, selector valve means responsive to the liquid level in the sump means, operative at a high predetermined level to open all of said return conduits, at each of a succession of progressively lower predetermined levels, to shut off a different one only of said return conduits and at a lowermost level to shut 05 all of said return conduits.

' HAROLD W. ADAMS.

EARL SCHUYLER. KLEINHANS. 

